/Engine/Source/Runtime/Core/Public/Async/TaskGraphInterfaces.h
"Complete" the event. This grabs the list of subsequents and atomically closes it. Then for each subsequent it reduces the number of prerequisites outstanding and if that drops to zero, the task is queued.
void DispatchSubsequents ( [ENamedThreads::Type](API\Runtime\Core\Async\ENamedThreads__Type) CurrentThreadIfKnown )